In recent years, the development of telecommunication networks has made large progress. Also, the traffic capacity and thus the data amount handled by such networks has considerably increased. One approach to cope with such a large data amount while still providing a high speed data transmission within such networks is to use the generally known ATM transmission concept (Asynchronous Transfer Mode).
In brief, according to the well known principles of ATM, the data to be transmitted are grouped into cells as a kind of data packets, supplied to an ATM network element at a respective input cell rate (depending on the type of transmission and/or connection), and output from the ATM element at an output cell rate which is predetermined for the ATM element. Such an ATM network element can be modeled as a buffer through which a plurality of incoming data cell streams (one per connection) are passed and the output is an output cell stream with a certain delay. Such a model is also referred to in literature as “leaky bucket” model.
However, with an increasing data amount to be handled and/or transmitted, the buffer capacity of the ATM network element becomes a limiting factor for the increase in the amount of transmitted data.
Thus, it has to be decided whether a new transmission connection can be admitted to be handled by the ATM network element and/or the ATM network. Such decision schemes are generally referred to as Connection Admission Control (CAC).
Connection Admission Control (CAC) has a key role when considering a maximum admissible load of the ATM network and a possible congestion (overload) in an individual network element or the whole network element. CAC methods should ensure that only those (new) connections are admitted which can be transmitted while assuring a certain level of Quality of Service (QoS).
Generally, any CAC method should be very quick and also effective. Various approaches have already been proposed in literature. However, if the method is a very effective one, i.e., one which may exploit the maximum capacity of the network, it will presumably be too slow as it needs too many calculations. In contrast thereto, if a speed optimized, i.e. a very fast method is implemented for CAC in the network, at least some capacity of the network will be wasted as it will never be used due to those fast methods being not so accurate. An optimum algorithm will have to compromise somewhere between those two extremes.
For example, K. Liu, D. W. Petr and C. Braun have proposed “A Measurement-Based CAC Strategy for ATM Networks”, published as an IEEE publication with number 0-7803-3928-2/97/. In this publication, a two-part CAC strategy is proposed including a network initiated renegotiation of UPC (Usage Parameter Control) parameters, based on the result of the network keeping track of an actual resource usage of the user traffic.
However, due to the complexity of the proposed CAC strategy, this approach may be classified as belonging to the first kind of above mentioned extremes, entailing the associated drawbacks.